Light-projecting glass.



Nn. 637,|45, Patented Nov. I4, i899. G. MOFF'AT 8Ll E. J. DUBBINS. LIGHT PROJECTING GLASS.

Application tiled June 9, 1899.;

UNTED STATES A ENT FFICEo GEORGE MOFFAT AND EDWARD JOHN DOBBlNS, OF PHlLADELPHI,

- PENNSYLVANA.

LIGHT-PROJECTlNG GLASS.

SPECIFICATION forming part of Letters Patent No. 637,145, dated November 14, 1899.

Application led J'nne 9, 1899. Serial No. 719,895. (No model.)

To @ZZ whom it may concern:

Be it known that We, GEORGE MOFFAT and EDWARD JOHN DOBBINs, citizens of the United States, and residen ts ot Philadelphia, Pennsylvania,have invented certain Improvements in Light-Projecting Glasses, ot which the following is a specication.

Our invention relates to that class ot lightprojecting glasses Which have upon one side a series of parallel prism-bars tor retracting or reiccting the light, the object ot our invention being to so construct such a lightprojecting glass that the iield trom which the same receives its light Will be enlarged and greater diffusion ot the light effected, so as to materially increase the area to which light is supplied by the glass.

In the accompanying drawings, Figure 1 is a perspective View ot a piece ot light-projecting glass constructed in accordance with our invention. Fig. 2 is a section ot the same on the line d d. Fig. 3 is a section on the line h l).

Our improved light-projecting glass has upon one side parallel prism-bars i and upon the opposite side parallel lens-bars 2, disposed substantially at a right angle in respect to the prism-bars, these lens-bars presenting outer convex faces, as shown in Fig. 1. ln the present instance each ot the prism-bars has a plane face 3 and a curved or lens-like tace 4, for a purpose explained hereinafter; but other forms ot' prism-bar may he used Without departing trom the lnain teature ot rour invention. The purpose ot such lensbars is to materially increase the ettective area ot the source trom which the glass derives its illumination, lateral rays being caught and transmitted by the convex surtaces ot the lens-bars, which would be lost by reflection from a ilat surface or troni a glass presentinga considerable area ot iiat surta-ce on the light-receiving side, all ot the rays, moreover, being retracted by the lens without that interference With each other which is au objection to light-projecting glasses in which some of the light is transmitted directly, While other rays are retracted and recause lateral diffusion ot the light projectedi by the glass, and thereby correspondingly increase the area which canbe effectively illu-'f lninated.

We Wish to avoid all internal reiiection trom the lens-surface ot the glass when said lens-surface is presented to the incident ray, and tor this reason the lens-bars are shallow or of such a considerable radius ot curvature that an incident ray striking any part ot the curved surface ot the lens-bar and retracted thereby cannot reach anyinternal surface ot the lens-bar so as to be re'iected, but will, atter retraction, pass directly through the glass until it reaches the opposite prism-surtace.

One ot the advantages of a light-projecting glass constructed in accordance with our invention is that it may be used effectively in the manner shoWn--that is to say, occupying a relation in respect to the upper portion otrthesvindpiv-opening which is the reverse of the usual awning or canopy position, thereby permitting the direct transmission ot light through the upper portion of the window-opening in addition to that which is projected therethrough by the glass, thus insuring the lighting ot an area close to the window andovercoining a detect in prismglasses as ordinarily used, which rob the areas near the Window-openings ot light tor the benefit ot the portions to which the latter is projected.

`Wemay state that one ot the incidental advantages ot our invention is that the lensbars very materially increase the strength ot the glass and permit us to produce glasses ot larger areathan is possible in making lightprojecting glasses of ordinary character.

Having thus described our invention, we claim and desire to secure by Letters Patent- A light-projecting glass, having upon one face a series ot prism-bars, and upon the other tace a series ot shallow lens-bars, disposed substantially at a right angie to the prisniour invention We have signed our names, in bars and presenting outer convex faces of presence of two Witnesses, this 2d day of 1o such radius of curvature that an incident June, 1809.

ray, striking any part of the convex surface, GEORGE MOFFAT. and retracted thereby, Will pass through the EDWARD JOHN DOBBINS. L glass Without reflection from an internal sur- Titnesses: face of the iens-bar, substantially as specified. FRANK N. BOOZ,

In testimony that We claim the foregoing as HENRY A. JAMES. 

